The predictability of expansion with Invisalign: A retrospective cohort study

• Published in: American journal of orthodontics and dentofacial orthopedics Vol. 163; no. 1; pp. 47 - 53
• Main Authors: Tien, Richard, Patel, Vraj, Chen, Tulrica, Lavrin, Igor, Naoum, Steven, Lee, Richard J.H., Goonewardene, Mithran S.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01-01-2023
• Subjects: Bicuspid; Maxilla; Molar; Orthodontic Appliances, Removable; Reproducibility of Results; Retrospective Studies
• ISSN: 0889-5406; 1097-6752
• DOI: 10.1016/j.ajodo.2021.07.032

Few studies have evaluated the predictability of expansion with Invisalign for the current SmartTrack material.
Pretreatment, predicted, and posttreatment digital models from Invisalign’s ClinCheck software were obtained for 57 adult patients with a planned arch expansion of at least 3 mm. Arch width measurements were collected using a software measuring tool (MeshLab), Invisalign’s arch width table, and the centroid of the clinical crown. Data for 30 patients were remeasured for each method to assess intrarater reliability. Predictability of expansion was calculated by comparing the amount of achieved expansion to predicted expansion.
The predictability of expansion across centroids for the maxillary teeth was: 72.2% canines, 78.9% first premolars, 81.1% second premolars, 63.5% first molars, and 41.5% second molars. The predictability of expansion across centroids for the mandibular teeth was: 82.3% canines, 93.0% first premolars, 87.7% second premolars, 79.8% first molars, and 42.9% second molars. The average expansion was significantly different from that predicted for each type of tooth in both the maxilla and mandible. Both underexpansion and overexpansion were observed. Arch width measurement reliability for each employed method was as follows: MeshLab (average error 0.197 mm); calculated centroids (0.002 mm); ClinCheck arch width table (0.000 mm).
On average, the amount of predicted expansion is not achieved with the Invisalign system and varies according to tooth type and arch. Discretion is required when overcorrecting to compensate for expansion inaccuracy. Both underexpansion and overexpansion were observed; further investigation into factors influencing underexpansion and overexpansion is required.
•The efficacy of clear aligners in the transverse plane was evaluated.•The mean accuracy of buccal transverse expansion in the maxillary arch was 76.4%.•The mean accuracy of buccal expansion in the mandibular arch was greater at 86.9% molars.•Underexpansion and overexpansion for all teeth, excluding second molars, were exhibited.•Overcorrection recommendations based on expansion inaccuracies must be considered cautiously.